Method for producing high weave density airbag fabric on a water-jet loom using unsized yarns

ABSTRACT

A method for forming an airbag fabric for use in protecting vehicle occupants during a collision. The airbag fabric includes at least a portion of fabric woven by water-jet weaving yarns without chemical sizing compounds thereon at weave constructions comparable to those available by traditional Rapier weaving processes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation-In-Part of our co-pending applicationSer. No. 08/219,989 filed Mar. 30, 1994 U.S. Pat. No. 5,421,378.

FIELD OF THE INVENTION

The present invention relates generally to the construction of airbagsand airbag fabrics for use in restraining vehicle occupants duringcollisions and more particularly to airbags formed from water-jet wovenfabrics unsized yarn woven at high densities.

BACKGROUND

Airbag equipment installed on a fixed portion of an automobile or anairplane body in front of a seated occupant plays an important role inthe protection against injury arising due to collision with the fixedportion of the car body or airplane during an accident. Airbags may beproduced in a number of manners and from a number of differentmaterials. However, airbags are typically formed, at least in part, fromsome type of woven textile material. Such textile materials aredisclosed in Sollars, Jr. U.S. Pat. Nos. 5,277,230 to Sollars, Jr.issued Jan. 11, 1994; 5,259,645 to Hirabayashi, et al. issued Nov. 9,1993; 5,110,666 to Menzel, et al. issued May 5, 1992; 5,073,418 toThornton, et al. issued Dec. 17, 1991; 5,011,183 to Thornton, et al.issued Apr. 30, 1991; 4,921,735 to Bloch issued May 1, 1990; and3,814,141 to Iribe, et al. issued Jun. 4, 1974. The teachings of all ofwhich are incorporated herein by reference.

Historically, fabrics for use in vehicle airbags have typically beenformed using conventional Rapier weaving machines wherein the pick yarnis drawn mechanically across the warp. Such weaving practices have beensuccessful in producing the high weave density, i.e. pick count, whichis desired for structural stability in the fabric used to withstandinflation and collision forces when the airbag is deployed during anaccident. Unfortunately, typical Rapier weaving machines aresignificantly slower than alternative weaving technology such aswater-jet weaving.

In water-jet weaving, the pick yam is drawn through the shed of the warpyarns by means of a stream of water which represents a much fastermethod of insertion than the mechanical Rapier. Heretofore, airbagfabrics incorporating yarn of approximately 420 denier have been wovenon water-jet weaving machines at a maximum weave density ofapproximately 46×46 (warp×fill). Likewise, airbag fabrics incorporatingyarn of about 630 denier have been woven on water-jet weaving machinesat a maximum weave density of approximately 38×38 and airbag fabrics ofabout 840 denier or greater have been woven at a maximum weave densityof about 33×33. As will be appreciated by those with skill in the art,these constructions are lighter than the typical fabric woven onconventional Rapier weaving machines which would be about 49×49 for 420denier fabric, 41×41 for 630 denier fabric and 36×36 for 840 denier.Historically, in order to compensate for the lower weave densityachievable on water-jet weaving machines, the weaving has been performedusing yarns having high breaking tenacities so as to provide improvedstrength in the final fabric despite the lighter weave construction.

As will be appreciated by those of skill in the art, yarns of hightenacity may require slashing with a chemical compound referred to as asizing compound to enhance the mechanical integrity of the highertenacity yarns during weaving. When weaving fabric for airbags, the sizewhich is used is typically a polyacrylic acid although other polymerssuch as polyvinyl alcohol, polystyrene, and polyacetates may likewise beutilized. While the sizing compound is typically effective in enhancingthe mechanical integrity of the high tenacity yarn, such sizing alsotends to enclose yarn oils which may not be compatible with polymericcompounds used for coating the fabric prior to its formation into anairbag structure. Accordingly, the practice prior to the presentinvention has been to eliminate the sizing compound as well as theenclosed yarn oils by the scouring and drying of the fabric prior toeffecting any coating operation.

As will be recognized, the addition of scouring and drying operationsmay tend to increase the cost for the overall production of fabric.Thus, it is of useful benefit to provide a fabric which may be used inan airbag and which is woven on a water-jet loom at high weaveconstructions such as are available on conventional Rapier machineswhile avoiding the need to use high tenacity yarns with sizing compoundsapplied thereto. Such an improvement permits the complete elimination ofscouring the fabric to remove enclosed yarn oils since the oils areremoved within the water stream during the weaving process itself.

SUMMARY OF THE INVENTION

In light of the foregoing, it is a general object of the presentinvention to provide an airbag and airbag fabric for use in protectingvehicle occupants during a collision, comprising at least a portion offabric woven by means of water-jet weaving at a weave constructioncomparable to that available by traditional Rapier weaving machines.

In that respect, it is an object of the present invention to provide anairbag and airbag fabric comprising at least a portion of woven fabricformed by means of water-jet weaving unsized yarn of about 630 denier orgreater wherein such woven fabric has a weave construction of about 39threads per inch or greater in both the warp and the fill directions.

It is a related object of the present invention to provide an airbag andairbag fabric comprising at least a portion of woven fabric formed bymeans of water-jet weaving unsized yarn of about 840 denier or greaterwherein such woven fabric has a weave construction of about 34 threadsper inch or greater in both the warp and the fill directions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview perspective of a water-jet weaving machineillustrating several machine modifications believed to enable theproduction of fabrics having high weave densities on such machines;

FIG. 2 illustrates equipment modifications to the weft cutting and catchselvage take-off for the right selvage waste removal of the water-jetweaving machine illustrated in FIG. 1;

FIG. 3 is a side profile schematic of the weaving machine shown in FIGS.1 and 2 including the off-loom take-up assembly therefor;

FIG. 4 is a cut-away side view taken generally along line 4--4 of FIG. 2and illustrating the high-profile bar temple assembly;

FIG. 5 shows a plain weave fabric formed according to the method of thepresent invention;

FIG. 6 is a schematic cross-section view of a typical airbaginstallation mounted in a steering wheel; and

FIG. 7 is a schematic view showing the airbag of FIG. 6 in an expandedcondition.

While the invention may be described and disclosed in connection withcertain preferred embodiments and procedures, it is in no way intendedto limit the invention to any such specific embodiments. Rather, it isspecifically intended to cover all embodiments and modifications as mayfall within the true spirit and scope of the invention as defined by theclaims appended hereto.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS

Now looking to the FIGURES wherein like reference numerals denote likecomponents in the various views, in FIG. 1 there is shown a water jetweaving machine 10 such as a Nissan type LW541 or LW542 available fromthe textile machinery division of the Nissan Motor Company Ltd.including a base structure 11, for use in delivery of a plurality ofwarp yarns 12 from a warp beam 14. As illustrated in FIG. 1 and FIG. 3,the warp yarns 12 are passed over a tensioning roll apparatus 18 whichis used to adjust the warp tension as described more fully below.

As will be appreciated, approximately half of the warp yarns 12 arepassed through a first harness mechanism 24 and approximately half ofthe warp yarns 12 are passed through at least a second harness mechanism26. As best illustrated in FIG. 3, the first and second harnessmechanisms 24, 26 may be moved up and down with respect to one anotherso as to adjust the opening or "shed" between the two sets of warp yarnsin an alternating manner. By shifting the respective position of eachset of warp yams, a water-jet nozzle 28 may be used to insert a fillyarn 30 on a periodic basis in the shed between the two sets of warpyarns. By coordinating the insertion of the fill yarn 30 with thereciprocating movement of the first and second harness mechanisms 24, 26a woven structure with the fill yarn overlying and underlyingalternating warp yarns may be achieved.

It will be appreciated that once the fill yarn 30 is inserted inappropriate orientation with respect to the warp yarns 12, it isnecessary to secure these yarns in place in a relatively securestructure by forcing them against the previously inserted fill yarns bymeans of a beating process as carried out by a reciprocating reed 31which separates the warp yarns at the point of fill yarn insertion andbeats the fill yarns into place at the bar temple 32 as discussed morefully below in relation to FIG. 4.

As will be readily appreciated by those of skill in the art, once thefill yarn is inserted, it must be cut off at the boundary of the fabricbeing produced and removed along with the selvage waste. As bestillustrated by reference to FIGS. 1 and 2, the cutting at both the rightand the left sides of the fabric is preferably performed by means of hotknife cutters 34 based on electrical resistance as opposed to mechanicalscissors which have heretofore been utilized. The yarn cut is entrainedin the catch cord 36 by suction produced behind a catch plate 38 throughvacuum line 40 by a suction pump (not shown). The catch cord with theentrained fill yarn is thereafter passed through a twister head 42 forselvage waste accumulation.

As indicated previously, it is an object of the present invention toprovided a water-jet woven fabric with a high pick count. That is, thefabric has a high density of threads in both the warp and the weftdirection. Specifically, the present process produces a fabric with aweave density of greater than about 38 threads per inch and preferablybetween about 39 and 43 threads per inch in both the warp and the filldirection while preferably using yarn having no sizing compound thereonof about 680 denier or less. While similar weave densities have beenpossible using Rapier weaving machines, prior to the present inventionwater-jet weaving could only achieve weave densities in this range usingyarn of less than about 630 denier. Specifically, it is believed thatprior to the present invention yarn of less than about 580 denier wasneeded to achieve a weave density of 43 threads per inch while less thanabout 630 denier was needed to achieve a weave density of 38 threads perinch. The present practice thus provide a closer packing of higherdenier yarns.

A weave density of greater than 33 threads per inch and preferably 34 to36 threads per inch may be produced in the present process using yarn upto about 870 denier. It is believed that prior to the present invention,such weave densities could only be achieved in water-jet weaving throughuse of yams of less than about 840 denier. Specifically, it is believedthat prior to the present invention, yarn of less than about 810 denierwas needed to achieve a weave density of 36 threads per inch while lessthan about 840 denier was needed to achieve a weave density of 33threads per inch.

The present practice thus permits fabric to be woven from 420 denieryarn at a density of about 47 threads per inch or greater; from 630denier yarn at a density of about 39 threads per inch or greater; andfrom 840 denier yarn at a density of about 34 threads per inch orgreater.

In one important aspect, it has been determined that increased warptension beyond that previously used on water-jet weaving machinesfacilitates in the production of such high weave density fabrics. By wayof example only, and not limitation, it has been determined thatincreasing the warp tensioning from the standard level of about 60 gramsper inch to a level of between about 80 and 95 grams per inch issuccessful in increasing the weave density significantly. As illustratedin FIG. 3, this warp tension is adjusted by adding or removing warptensioning weights 43 to a tensioning lever arm 44 which, in turn,increases or reduces the tension on the tensioning roll apparatus 18previously discussed.

As will be readily appreciated by those of skill in the art, asubstantial increase in the tension of a large number of warp yarnssignificantly increases the forces necessary to beat the fill yarn intoplace. Accordingly, it has been found beneficial to incorporate severalfurther modifications to the water-jet weaving machine as illustrated inFIGS. 1, 2 and 4 to accommodate these higher stresses. In particular, ithas been found that the use of a so called high profile bar temple 32utilizing a chrome or anodized aluminum casing 46 and a nylon threadedrod 48 (FIG. 4) provides the best performance and durability in handlingthe high warp tension stresses. One bar temple which may be particularlypreferred is available from the Lewis P. Batson Company whose address isbelieved to be 1 Club Road, Box 3978, Greenville, S.C. 29608.

The high profile bar temple 32 is preferably supported by a plurality oftemple support brackets 52 extending between the breast beam 54 of theweaving machine and a rear support arm 53 of the bar temple 32. Asshown, the breast beam 54 is preferably connected to the frame 11 of theweaving machine by a high strength breast plate 56 using connecting pins58. In the potentially preferred embodiment, the connecting pins 58 willbe at least 3/8 inch in diameter so as to prevent deflection duringmachine beat-up. It is to be noted that it has also been foundbeneficial to increase the width of the catch plate arm 60 from thestandard width of 10 millimeters to a width of about 25 millimeters tocontain any potential fill deflection due to insertion through a highertension warp.

It is to be understood that following the beating action by the reed 31at the bar temple 32, a woven fabric 70 is formed having yarns runningin both the warp and the fill direction. In a potentially preferredembodiment, the overall pick count as measured in the fill direction maybe substantially equivalent to the pick count measured in the warpdirection thus yielding a plain weave as shown in FIG. 5.

As indicated previously, in the preferred embodiment, both the warpyarns 12 and the fill yarns 30 will be nonsized. By the term "nonsized"is meant that no sizing compound such as polyacrylic acid, polyvinylalcohol, polystyrene, polyacetates, starch, gelatin, oil or wax isapplied to enhance coherency to the filament. By way of example, and notlimitation, suitable warp and weft yarns used in the fabric of thisinvention are multifilament yarns formed from polyamides such as nylon 6and nylon 6,6 as well as polyesters, and polyacrilonitrile. Nylon 6,6may be preferred. In the preferred embodiment, the multifilament yarnused in both the warp and the fill direction will be a flat filament,high entanglement yarn using a proprietary finish oil available fromE.I. DuPont in Wilmington, Del. under the trade designation K-7389. Bythe term "flat filament" is meant a nontextured yarn wherein theindividual filaments have not undergone any random interlacing thereofsuch as through the application of an external fluid force.

Looking again to FIG. 3, after the woven fabric 70 is formed it ispassed over and around a plurality of take-up rolls 80, 81, 82 andthereafter passed to through an accumulator 84 by conveyor rolls 85-90.Importantly, it has been found beneficial to maximize the weight 92 onthe take-up compensator arm up to a level of about 80 pounds. It hasalso been found beneficial to the reduction of creases to apply acombination of radiant and convective heat to the fabric 70 by means ofa heater 94 just prior to placing the fabric on a removal roll 96. Onesuch heater which is believed to be particularly suitable is a 4,000watt Radiant unit model number PO-370AX26 with a model 965 control unitavailable from Watlow Industries whose business address is believed tobe 12001 Lackland Road, St. Louis, Mo. 63146.

While the fabric of the present invention may be useful for a number ofapplications, this fabric is believed to be particularly useful forincorporation in automobile restraint cushions or airbags. As will beappreciated by those of skill in the art, such airbags oftentimesutilize a fabric coating to control permeability. In order to apply suchcoatings, however, sizing compounds such as polyacrylic acid as well asyarn oils entrapped by those sizing compounds must first be removed fromthe fabric by scouring and drying operations. Through the use ofnonsized yarn, this scouring operation can now be completely eliminatedsince yarn oils are no longer entrained but may now be removed in thewater-jet weaving process. Prior to the present invention, there was noknown process available for the production of high weave density airbagfabrics using yarns free of sizing compounds. Specifically, the use ofRapier or air-jet weaving machines with yarns having no sizing compoundthereon leads to unacceptable yarn damage from the heat build-up andabrasion caused by the contact of the warp ends with moving partsinserted into the warp shed during the weaving process. The use ofwater-jet weaving avoids yarn damage due to heat build-up since the warpyarns are not in contact with moving parts during insertion of fill yarnthrough the warp shed. Accordingly, such water-jet woven fabricsrepresent a useful advancement over the prior art.

FIGS. 6 and 7 are merely representative of one type of usage and designfor an airbag 103 which it will be understood preferably opens inopposing relation to a vehicle occupant 105 in the event of a collision.In the embodiment illustrated, the airbag 103 is fixed at its base to aninflator 107 which in turn is linked to a collision detection sensor(not shown). When the deceleration of the vehicle exceeds a certainlevel, the collision detection sensor sends a signal to the inflator 107thereby inducing the chemical reaction of a gas generating agent toinflate the airbag 103 from the stowed position of FIG. 6 to theinflated position illustrated in FIG. 7. In the illustrated embodimentthe airbag 103 is stowed in a steering wheel 109 although it is to beappreciated that the airbag 103 could also be positioned in any otherlocation opposing a vehicle occupant including a dash panel, door panelor forward seat.

It is to be understood that the herein disclosed fabric construction maybe used in various portions of the airbag where it is desired tomaintain tear resistance and to control the flow of the inflation gaseswhich enter the airbag during collision. Thus, coated and uncoatedvariations of the fabric may be used either as a face fabric where it isdesired to have low permeability, at the back of the bag where higherpermeability may be desired or at the sides of the bag where apreselected controlled degree of permeability may be desired. Moreover,that fabric which is used may be used directly without the need for anyscouring operation prior to coating or formation into the airbag.

In accordance with the above description, it is seen that the presentinvention provides a fabric and airbag formed therefrom wherein thefabric is woven on a water-jet weaving machine at weave densities whichhave previously been achievable only on Rapier weaving machines. Whilespecific embodiments of the invention have been illustrated anddescribed, it is to be understood that the invention is not limitedthereto, since modifications may be made and other embodiments of theprinciples of this invention will occur to those skilled in the art towhich this invention pertains. Therefore, it is intended by the appendedclaims to cover any modifications and other embodiments as incorporatethe features of this invention within the true spirit and scope of suchclaims.

What is claimed is:
 1. A method for water-jet weaving a high weavedensity fabric for use in a vehicle airbag, the method comprising thesteps of:(a) conveying a plurality of warp yarns having a denier ofabout 630 or greater with no chemical sizing compound thereon through awater-jet weaving machine; (b) inserting a plurality of fill yarnshaving a denier of about 630 or greater with no chemical sizing compoundthereon between said plurality of warp yarns by means of a water-jetsuch that any yarn oils are at least partially removed by said waterjet; and (c) beating said plurality of fill yarns into place betweensaid warp yarns such that a fabric having a weave density of about 39threads per inch or greater is produced.
 2. The invention as in claim 1,wherein said fabric has a weave density of about 39 to 43 threads perinch.
 3. The invention as in claim 1, wherein said warp yarns have adenier of between about 630 and about
 680. 4. The invention as in claim3, wherein said fill yams have a denier of between about 630 and about680.
 5. A method for water-jet weaving a high weave density fabric foruse in a vehicle airbag, the method comprising the steps of:(a)conveying a plurality of warp yarns having a denier of about 840 orgreater with no chemical sizing compound thereon through a water-jetweaving machine; (b) inserting a plurality of fill yarns having a denierof between about 840 or greater with no chemical sizing compound thereonbetween said plurality of warp yarns by means of a water-jet such thatany yarn oils are at least partially removed by said water jet; and (c)beating said plurality of fill yarns into place between said warp yarnssuch that a fabric having a weave density of about 34 threads per inchor greater is produced.
 6. The invention as in claim 5, wherein saidfabric has a weave density of about 34 to 36 threads per inch.
 7. Theinvention as in claim 5, wherein said warp yarns have a denier ofbetween about 840 to about
 870. 8. The invention as in claim 7, whereinsaid fill yarns have a denier of between about 840 to about 870.